Sliding Joint for Use with a Downhole Tool

ABSTRACT

A mount for use with a downhole tool such as, but not limited to, an electrical submersible pump (“ESP”) gauge, includes a mounting means that does not use a fixed- or spring-connection between it and the outer housing of the sensitive assembly but rather makes use of a sliding joint. One end of the sliding joint is in communication with the sensitive assembly of the downhole tool and the other end of the sliding joint is in communication with another component of the downhole tool. The sliding joint is arranged relative to the sensitive assembly so that a radial movement of the sliding joint is restricted and an axial movement of the sliding joint is permitted. When in use, the sliding joint isolates the sensitive assembly from an axial load, thermal stress, or both axial load and thermal stress.

BACKGROUND OF THE INVENTION

This invention relates generally to devices used to prevent elongation and stress loading of sensitive components of a downhole tool such as, but not limited to, the electronic components of electrical submersible pump (“ESP”) gauges and to maintain sensitive component integrity under high tensile loads and large thermal expansions. The sensitive component is typically the electronics associated with a gauge, but could be any component where high tensile loading is undesirable (e.g., the choke assembly of the gauge). The following disclosure uses an ESP gauge as an exemplar downhole tool which has sensitive components.

Prior art shows ESP gauges use a fixed connection between the outer housing and the electronics on both ends of the gauge. Other gauges use a spring design inside the outer housing to allow for tolerance stack up and minimal thermal expansion. Both designs do not completely isolate the electronics from load transferred by the outer housing.

If a gauge with the fixed connection is introduced to high tensile load or has significant varied thermal expansion occur between different materials (or both high tensile load and varied thermal expansion), load is transferred between the outer housing and the electronics and the choke assembly. Gauges using a spring connection are not completely free of induced loading, as the spring itself can transfer load from the outer housing to the electronics and the choke assembly. In the spring connection design the electronics are not supported as well radially about the gauge as in the fixed connection design.

Because the fixed- and spring-connection designs transfer load to the electronics, neither design is ideal when the gauge is required to carry high tensile loads. Therefore, a need exists for a system and method of attaching an electronics module and choke assembly to the outer housing of a downhole pressure gauge to allow for high tensile loading of the housing (e.g., typically about 10,000 lbs and above) without transferring the load to the sensitive components. The system and method will also eliminate extra stress on the sensitive components produced by the outer housing due to dissimilar heat expansion of the metals.

SUMMARY OF THE INVENTION

A mount made according to this invention for use with a downhole tool such as, but not limited to, an electrical submersible pump (“ESP”) gauge includes a mounting means that does not use a fixed- or spring-connection but rather makes use of a sliding joint. The sliding joint is configured at one end to receive the electronics module or the choke assembly of the downhole tool and the other end is in communication with a head (or base) of the downhole tool.

The sliding joint is arranged relative to the gauge so that a radial movement of the sliding joint is restricted (i.e., head of the downhole tool, the sliding joint, and gauge are kept centered relative to one another) and an axial movement of the sliding joint is permitted. Unlike the prior art designs, the sliding joint isolates the electronics module and the choke assembly from an axial load when the gauge is in use.

Objects of this invention are to provide mounting means for a downhole tool which (1) allows for independent axial elongation of the outer housing and sensitive components while still supporting the radial load and without inducing stress into the sensitive components; (2) can be used in retrofit applications; (3) in the case of ESP applications, can be used with an inverted ESP motor setup (i.e., gauge mounted above the motor); and (4) can be used to reduce or eliminate the negative effects of thermal expansion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a preferred embodiment of a mounting means made according to this invention for an exemplar downhole tool, an electrical submersible pump (“ESP”) gauge. The mounting means is both fixed- and spring-connection free and includes a sliding joint which can be made up of a head adapter and choke adapter. The connection between the two adapters allows for sliding movement in an axial direction. This particular embodiment is intended primarily for retrofit applications but can also be used in new applications.

FIG. 2 is an isometric exploded view of the mounting means of FIG. 1. The connection between the two adapters restricts or prevents movement in a radial direction.

FIG. 3 is an isometric view of the choke adapter of FIG. 1. The electronics module of the ESP gauge connects to a choke assembly which, in turn, mounts to a flange end of the choke adapter. An O-ring groove on the choke adapter receives an O-ring which cushions load and vibration and allows clearance for assembly tolerance stack up along the length of the gauge.

FIG. 4 is an isometric view of the head and head adapter of the mounting means of FIG. 1. The head adapter mounts to the head using conventional fastening means.

FIG. 5 is a cross-section view of the mounting means of FIG. 1. The head adapter and sliding choke adapter include means for self-aligning one to the other. The preferred self-aligning means is a lead-in chamfer on both adapters.

FIG. 6 is an isometric view of a choke assembly mounted to the choke adapter of FIG. 1.

FIG. 7 is an isometric view of the mounting means of FIG. 1 connecting the choke assembly to the head via the sliding joint.

FIG. 8 is another preferred embodiment of the mounting means which makes use of a counterbore.

FIG. 9 shows another preferred embodiment of the mounting means. The O-ring rests directly on the housing, thereby eliminating the need for the head adapter.

FIG. 10 is yet another preferred embodiment of the mounting means. Unlike the embodiment of FIG. 1, the head and head adapter are combined into a single head end. This particular embodiment is intended primarily for non-retrofit applications.

FIG. 11 is still yet another preferred embodiment of the mounting means. The head and head adapter are combined into a single head end, as is the choke insulator and choke adapter which are combined into a single choke end. Like the embodiment in FIG. 10, this particular embodiment is intended primarily for non-retrofit applications

Elements and Element Numbering Used in the Drawings 15 Outer housing 17 Inside diameter 20 Mounting means 25 Sliding joint 30 Choke adapter 33 Tapered portion 35 Outside diameter 37 O-ring groove 39 O-ring 50 Head adapter 53 Tapered portion 55 Counterbore 70 Head 71 Screw holes 75 Tapered portion 77 Inside diameter 80 Choke assembly 85 Choke insulator 87 Choke end (combined choke adapter 30 and choke insulator 85) 90 Head end (combined head 70 and head adapter 50) 97 Inside diameter wall surface

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 7, a mounting means made according to this invention for an electrical submersible pump (“ESP”) gauge includes a mounting means 20 for the sensitive components of the gauge (e.g., an electronics module (not shown)) that does not include or rely upon a fixed- or spring-connection but rather makes use of a sliding joint 25. For the purpose of this disclosure the sensitive components are components, including but not limited to electronics and the choke, housed in an outer housing of a downhole tool and which are not designed or intended to carry loads. The sensitive components, which may be part of a sensitive assembly, are susceptible to intermittent malfunction and permanent damage because of heat, temperature, vibration and load, and typically are the components which determine the overall reliability of the tool.

In a preferred embodiment, which is intended primarily for retrofit applications, the sliding joint 25 includes a choke adaptor 30 and a head adapter 50. Preferably, the head adapter 50 is configured so that it may be affixed to prior art heads 70 by using the existing screw holes 71 in the head 70 Similarly, the choke adapter 30 is configured so that it mounts to the choke assembly 80 using the existing screw holes (not shown) of the choke assembly 80

The outside diameter 35 of the choke adapter 30 includes an O-ring groove 37 for receiving an O-ring 39 (see FIG. 3). The O-ring 39 is preferably an elastomeric O-ring to cushion the joint and provide clearance for tolerance stack up, but metal-to-metal or plastic joints (e.g., including but not limited to bronze bushings, plastic bushings, metal bearings, to name a few) could also be used.

The relationship between the head 70, head adapter 50, and the choke adapter 30 is such that it self-aligns for ease of assembly. The relationship also restricts movement in the radial direction but, because of the choke adapter 30, permits movement in an axial direction, thereby relieving the sensitive components of any tensile load or stress. Preferably, movement in the radial direction is restricted to no more than 1/16 of an inch (˜1.58 mm) and, more preferably, to no more than 1/32 of an inch (˜0.79 mm). In one embodiment, movement in the radial direction is no greater than 1/64 of an inch (˜0.40 mm). The sliding joint 25 can be solidly mounted at either end of the choke assembly 80 or the electronics module, thereby making it useful as a mounting means 20 in ESP applications where the gauge is mounted above the ESP motor.

The head 70 includes a tapered portion 75 that receives a complementary tapered portion 53 of the head adapter 50 (see FIG. 5). The head adapter 50 is then supported inside the inside diameter 77 of the head 70. One of the benefits of this tapered design is that it supports prior art gauges without requiring major modifications. The tapered portion 75 in the head 70 aligns the head adapter 50 radially so that the head adapter 50 and head 70 are concentric with one another. The choke adapter 30 also includes a tapered portion 33. Tapered portion 33 (or lead-in chamfer) self-aligns the choke adapter 30 and the head adapter 50.

In an alternate embodiment (see FIG. 8), the head 70 includes a counterbore 55 which can be used to align the head 70 and head adapter 50 with one another. Compared to the tapered arrangement, the counterbore arrangement eliminates any gap between the head 70 and the head adapter 50 caused by the tolerance stack up in the tapered section.

The above embodiment, which uses a head adapter 50, is intended to allow for existing components to be retrofitted with this design. For new designs, there are alternative concepts which eliminate the need for the head adapter 50 and use a single piece head 90 (see FIGS. 9, 10 and 11).

For example, in an alternate embodiment of the mounting means 20, the O-ring 39 slides on the inside diameter 17 of the outer housing 15 without the need for the head adapter 50 (see FIG. 9). This particular embodiment reduces the number of parts but may also increase the chance of damaging the O-ring 39 during installation, especially if the inside diameter 17 of the outer housing 15 has not been properly machined, honed or polished.

In another alternate embodiment of the mounting means 20, the head 70 and head adapter 50 are combined into a single piece head end 90. The inside diameter 97 of the head end 90 is configured so that the O-ring 39 slides on the inside diameter 97 of the head end 90 without the need for the head adapter 50 (see e.g., FIG. 10).

In yet another preferred embodiment, the head 70 and head adapter 50 are combined into a single piece head end 90, as is the choke insulator 85 and choke adapter 30 which are combined to form choke end 87 (see FIG. 11). This design has the advantage of fewer parts and does not require mounting screws. Like the embodiment in FIG. 10, this embodiment is intended primarily for non-retrofit applications.

While preferred embodiments of a mounting means for an ESP gauge have been described, certain modifications can be made by persons of ordinary skill in the art by making use of equivalent elements to those recited in the following claims and without those modifications, or the modified design, departing from the scope of the claims. 

What is claimed:
 1. A mount for use with a downhole tool, the mount comprising: a sliding joint configured at one end to be in communication with a sensitive assembly of the downhole tool and configured at the other end to be in communication with a component of the downhole tool; the sliding joint being configured so that a radial movement of the sliding joint is restricted and an axial movement of the sliding joint is permitted; the sliding joint when in use isolating the sensitive assembly from an axial load.
 2. A mount according to claim 1 further comprising at least one adapter, the at least one adapter being configured to receive one end of the sliding joint.
 3. A mount according to claim 2 further comprising the at least one adapter being a head adapter.
 4. A mount according to claim 2 further comprising the at least one adapter being a choke adapter.
 5. A mount according to claim 2 further comprising the at least one adapter having self-aligning means.
 6. A mount according to claim 5 further comprising the self-aligning means being a lead-in chamfer.
 7. A mount according to claim 5 further comprising the self-aligning means being a tapered portion.
 8. A mount according to claim 1 further comprising the sliding joint being housed in an outer housing of the sensitive component.
 9. A mount according to claim 1 further comprising means to dampen vibration of the sliding joint.
 10. A mount according to claim 9 wherein the dampening means is an O-ring located on an outside diameter of the sliding joint.
 11. A mount according to claim 1 wherein the mount is fixed-connection free relative to the outer housing.
 12. A mount according to claim 1 wherein the mount is spring-connection free relative to the outer housing.
 13. A mount according to claim 1 wherein the sensitive component is at least one of an electronic component and a choke assembly.
 14. A mount for use with a downhole tool, the mount comprising: a sliding joint configured to connect one end of the downhole tool to a sensitive assembly of the downhole tool; the sliding joint, when connected between the sensitive assembly and another component of the downhole tool, isolating the sensitive assembly from an external load while maintaining a coaxial alignment between the sensitive assembly and the one end of the downhole tool.
 15. A mount according to claim 14 wherein the mount is fixed-connection free to an outer housing of the sensitive assembly.
 16. A mount according to claim 14 wherein the mount is spring-connection free to an outer housing of the sensitive assembly
 17. A system for isolating from an axial load one or more sensitive components associated with a downhole tool, the system comprising: a mount including a first means for placing one end of the mount in communication with a head or base of the downhole tool and a second means for placing the other end of the mount in communication with a sensitive assembly; the mount when in use maintaining an alignment between the downhole tool and the sensitive assembly as the mount moves between a first axial position and a second axial position and isolating the one or more sensitive components of the sensitive assembly from an axial load. 